In wireless communication systems, particularly cellular radio communication systems, mobile stations operating on a network may communicate via an air interface with a base transceiver station (BTS) and in turn with a base station controller (BSC). The BSC may also be coupled with a mobile switching center (MSC). Further, the BSC may be coupled with packet data serving element (PDSN) or other gateway, which may provide connectivity with an IP network, such as the public Internet or a private intranet (e.g., a wireless carrier's core IP network). The mobile station may thus communicate with entities on the IP network via a communication path comprising the air interface, the BTS, the BSC and the PDSN.
A properly equipped mobile station can initiate packet-data communication by sending a packet-data origination request message over an air interface access channel, and via the BSC, to the MSC. Applying industry standards, the origination request message may include a “packet data” service option code that characterizes the requested communication as packet-data communication, as compared with traditional voice communication. When the MSC receives the origination request, it may then detect the “packet data” service option code and responsively send the message back to the BSC for handling. (Note that, commonly, the MSC and BSC may be physically co-located and perhaps integrated in a common entity, sometimes referred to as an MSC/BSC or simply “switch.”)
In turn, when the BSC receives an origination request, the BSC may establish a radio link layer connection with the mobile station by assigning the mobile station to operate on a particular traffic channel over the air interface (e.g., a fundamental traffic channel, and perhaps one or more supplemental channels). In addition, the BSC may pass the origination request to the PDSN. The PDSN and mobile station may then negotiate with each other to establish a data-link layer connection, typically a point-to-point protocol (PPP) session over which packet data can be communicated between the mobile station and the PDSN. As part of this process, the mobile station may obtain an IP address, to facilitate packet communications. For instance, the PDSN may assign an IP address to the mobile station, or the PDSN may communicate with a mobile-IP “home agent” to obtain an IP address for mobile station. (Note that it may also be possible for a mobile station to engage more directly in packet-switched communications, rather than communicating packet data through a channelized PPP connection. For instance, the BSC itself might sit as a element on an IP network, and the mobile station might send and receive individual packets via the BSC.)
In most wireless communication systems like this, the radio-link layer connection with a mobile station may time-out after a predefined period of inactivity. For instance, after 10 seconds in which no data is communicated to or from the mobile station over the air interface, the BSC or the mobile station may “tear-down” the radio-link layer connection by releasing the traffic channel that had been assigned to the mobile station. At the same time, however, the data-link layer (e.g., PPP) connection with the mobile station might remain.
Once the radio-link layer connection with a mobile station has timed out, the mobile station will be considered “dormant.” However, if its data-link layer connection still exists, the mobile station may still seek to send packet data to other entities, and other entities may seek to send packet data to the mobile station. When another entity seeks to send packet data to the mobile station, the BSC may page the mobile station over an air interface paging channel. When a dormant mobile station receives a page indicative of an incoming data communication, or if the dormant mobile station seeks to send data, the radio link layer connection with the mobile station will need to be reestablished. To do so, the mobile station may send a message to the BSC over the access channel, requesting radio-link resources, and the BSC may then assign a traffic channel. The mobile station may then send or receive packet data over that traffic channel.
Some mobile stations may be equipped to automatically enter into an “always-on” data session upon power up, so as to provide IP network connectivity similar to that available through today's broadband landline modems. In particular, such a mobile station may be programmed to automatically send a “packet data” origination request upon power up and to then negotiate with the PDSN to establish a PPP session. After an initial period of inactivity, the radio-link layer connection with the mobile station may time-out. But, as indicated above, the mobile station may then acquire a radio-link connection when desired.
A mobile station that lacks both a radio-link and a data-link is considered to be in an “idle” state, contrasted with a “dormant” state. In the idle state, in order for the mobile station to engage in packet-data communication, it may conventionally send a packet data origination request in the manner described above.
Using packet-based communications, a mobile station may participate in data communications with other mobile stations operating on the wireless communication network via a variety of communication options and protocols. For examples, a mobile station may send and receive short messaging service (SMS) messages. As defined by TIA/EIA 637-A and/or other industry standards, a short messaging service center (SMSC) may operate on the wireless communication system network to receive, store and forward short messaging service messages to SMS-capable mobile stations. Additional communications options and protocols are possible as well, such as multimedia messaging service (MMS) messages, Real Time Protocol (RTP) communications, and e-mail messaging.